A galaxy and the Milky Way contains hundred of billion of stars, and a substantial amount of baryonic
gas [1]}, [2]} and
it is not possible directly to obtain the Newtonian dynamics of a galaxy with this number of objects. Instead, we have simulate
models of small ”galaxies" of hundred of objects in
orbits around their center of gravity, and in an expanding space with various strength of the expansion.
A recent article describes how to create
a collection of objects with rotation about their center of gravity by Molecular Dynamics (MD) simulations, obtained by an extension of
Newton's discrete algorithm [3]}. The algorithm is further developed to also include the Hubble expansion of space,
and the algorithm with
the extensions are given in the Appendix.
